Television receiving lamp



Feb. 27, 1934. D. D. KNOWLES TELEVISION RECEIVING LAMP Filed Feb. 5,1929 90 7: Neon [0%Hydrogesn.

Fig 2.

INVENTOR DeweyD. Know/ea ATTORN EY Patented Feb. 27, 1934 UNITED STATESPATENT OFFICE 11 Claims. (01. 176-122) My invention relates toglow-discharge lamps and particularly to glow-discharge lamps employedin the transmission and reproduction of pictures and sound.

One object of my invention is to provide an improved light source forsystems which require a luminous flux which follows instantaneously thefluctuations of an electrical control current.

Another object of my invention is to provide a luminous discharge devicein which the luminosity will disappear instantaneously when theelectrical or other exciting force falls to zero.

Another object of my invention is to provide a source of light having acharacteristic color which lies near the middle of the visible spectrumand which is capable of following with fidelity the instantaneousfluctuations of an electric field.

A further object of my invention is to provide a method of causing anexcited or ionized gaseous discharge path to return to an unionized orneutral condition instantaneously after the reduction to zero of theelectrical potential gradient to which it is subjected.

In the arts of television, and of recording sounds photographically, itis necessary to have a light source capable of-instantaneously followingfluc tuations of an electrical controlling quantity varying to the rateof hundreds of thousands of periods per second. It has, heretofore, beenattempted to employ gaseous electrical discharges as such light sources;and the electrical discharges through neon have proved, in general, bestadapted tothis purpose. In orderthat pictures and sound should bereproduced absolutely without distortion, it is necessary for the lightvariations to follow instantaneously upon variations of the electricalpotential gradient in the discharge path. I have found, however, that asa matterof fact, there is a perceptible time lag between thedisappearance of luminosity of a gas discharge in neon and the fallingto zero of the electric current therein; and I have also found a similarlag in the case of other similar gases. Such a time lag causes blearingof the image where pictures are being transmitted and causes distortionandunfaithful reproduction in the-case of photographic recording ofsound.

In accordance with my invention, I have dis covered that the time lagabove described can be substantially avoided if the vehicle throughwhich the electrical discharge passes comprises an admixture of neon, orone of the other suitable luminous gases with a small percentage ofhydrogen, or other gas, the molecule of which undergoes some change ofcondition not involving the emission of light within the range to whichthe optical system of the recording apparatus responds, and which occursat an energy level lower than that at which the luminous gas emitsuseful radiation. 0

As a specific instance of the foregoing principl the hydrogen molecule,which is normally diadischarge tube embodying the principles of myinvention; and

Fig. 2 shows a view thereof along the line 11-l1.

Referring to the above-mentioned figures of the drawing, a vacuum-tightenclosure 1 which may conveniently be. of glass has a stem 2 throughwhich are fused the inleading wires 3, 4 in a manner well-known in theart. The ends of the in-leading wires 3, 4, respectively, support twoplate electrodes 5, 6 which may be of a metal such as nickel or oftantalum and which are spaced apart by a distance preferablyconsiderably shorter than the mean-free path of an electron in thegaseous atmosphere about tobe described. The container 1 is exhausted toa high vacuum by methods which are standard in the lamp art and is thenprovided with an atmosphere which may have a pressure of ten to twentymillimeters of mercury.

In accordance with the principles of my invention, the aforesaid gaseousatmosphere may consist of a mixture of neon and hydrogen. I have foundthat if the mixture comprises 10% hydrogen and 90% neon, a desirableperformance is obtained, although considerable variations from theforegoing percentages may at'times be preferable, the precisecomposition of the gas, depending upon the particular purposes for whichthe lamp is to be employed.

Experiments have shown that the persistence luminosity whichcharacterizes electrical disployed in connection with a discharge tubein which the light is excited by impressing a potential differencebetween a pair of electrodes, similar advantageous results are found tofollow in the case of luminous discharges produced by high-frequencyinduction in tubes which are not provided with electrodes.

While I do not wishpmy invention considered dependent upon thecorrectness of the following theory, it is my belief that the immediateresponse of luminosity changeswitli variations of electrical gradient inthe gas is consequent upon the contact of the molecules of the luminousgas with another substance which absorbs the energy of their excitedstate almost instantaneously after it is attained and thereby preventsthe en-' ergy from being emitted further in the form of light quanta.Thus, in the particular embodiment herein described, an excited neonatom almost immediately collides with a diatomic hydrogen molecule. Itis a property of the latter that it may be split up into two atoms ofhydrogen with the absorption of an amount of energy somewhat less thanthat characteristic of the excited state of the neon atom; therebyabsorbing virtually all of the energy which otherwise the neon atomwould-emit as visible radiation. In consequence, every neon atom isreduced to the unexcited state very quickly after it has once beenexcited; and unless a potential gradient sufficient to continuouslyproduce reexcitation exists in the gas, the emission of visibleradiation ceases almost instantaneously.

While I have described neon as the particular luminous gas and hydrogenas the particular energy absorbing agent, it will be recognized that thesame principles may be applied to other luminous gases than neon andthat other energyabsorbing agents than hydrogen are applicable.

Thus the other noble gases and mercury vapor may be employed as theprincipal gas of the dis- I charge path.

' in a mercury vapor path may be quickly ended by the presence thereinof some agent, such as hydrogen, which has the property of absorbing theenergy required to dissociate the electron from the positive ion,without itself beingsplit up into electrically-charged components.

I claim as my invention:

1. An electrical-discharge device comprising an envelope containing anoble gas, electrodes therein spaced apart by a distance so small that apotential impressed across them causes a glow on one of said electrodesbut no glow between said electrodes, and a quantity of hydrogen mixedwith said noble gas.

2. An electrical-discharge device comprising an envelope containing anoble gas, electrodes therein spaced apart by a distance so small thatno glow appears between contiguous surfaces thereof when the lamp islighted, and a quantity of hydrogen mixed with said noble gas.

3. An electricaldischarge device comprising an envelope containing anoble gas, electrodes therein spaced apart by a distance less than themean-free path of an electron in said gas,

and a quantity of hydrogen mixed with said noble gas.

4. A gaseous-discharge device comprising an envelope, a plurality ofspaced-apart electrodes disposed within said envelope, and a mixture ofgases under reduced pressure surrounding said electrodes, said gasmixture being substantially 90% neon and 10% hydrogen and'the spacingbetween said electrodes being of the order of the mean-free path of anelectron in said gases,

whereby, upon the establishing of a potential difference between saidelectrodes, a glow appears upon one of the non-contiguous surfacesthereof and is responsive, without appreciable time-lag, to variationsin said potential.

5. An electrical-discharge device comprising an envelope containing aprincipal gas adapted, when excited, to emit light, electrodes thereinspaced apart by a distance so small that no glow appears betweencontiguous surfaces thereof when said gas is excited, and an admixturewith said gas of a substance having a critical energy level for a changeof physical state which is 7. An electrical-discharge device comprisingan envelope containing a principal gas adapted, when ionized, to emitlight, electrodes therein spaced apart by a distance less than themeanfree path of an electron in said gas, and an admixture with said gasof a substance having a critical energy level for a change of physicalstate which is less than the lowest energy level for ionization of saidprincipal gas.

8. An electrical-discharge device comprising an envelope containing aprincipal gas having a monatomic molecule, electrodes therein spacedapart by a distance less than the mean-free path of an electron in saidgas, and an admixture with said gas of a substance having a polyatomicmolecule.

9. An electrical-discharge device comprising an envelope containing aprincipal gas adapted, when excited, to emit light, having its maximumintensity near the middle of the visible spectrum, electrodes thereinspaced apart by a distance less than the mean-free path of an electronin said gas, and an admixture with said gas of a substance having acritical energy level for a change of physical state which is less thanthe lowest energy level for excitation of said principal gas.

10. An electrical-discharge device comprising an envelope containingneon, electrodes therein spaced apart by a distance less than themeanfree path of an electron in said neon, and an admixture with saidneon of a substance having a critical energy level for a change ofphysical state which is less than the lowest energy level for excitationof said neon.

11. An electrical-discharge device comprising an envelope containing aprincipal gas adapted, when excited, to emit light, electrodes thereinspaced apart by a distance less than the meanfree path of an electron insaid gas, and a quantity of hydrogen mixed with said gas.

DEWEY D. KNOWLES.

